1. Field of the Invention
This invention relates to a network for distributing signals and power around a gas turbine engine using a flexible harness. In particular, this invention relates to clips for holding a flexible harness for a gas turbine engine.
2. Description of the Related Art
A typical gas turbine engine has a substantial number of electrical components which serve, for example, to sense operating parameters of the engine and/or to control actuators which operate devices in the engine. Such devices may, for example, control fuel flow, variable vanes and air bleed valves. The actuators may themselves be electrically powered, although some may be pneumatically or hydraulically powered, but controlled by electrical signals.
Electrical power, and signals to and from the individual electrical components, are commonly transmitted along conductors. Conventionally, such conductors may be in the form of wires and cables which are assembled together in a harness. In such a conventional harness, each wire may be surrounded by an insulating sleeve, which may be braided or have a braided cover. The connections between the individual components and the conventional harness are made, for example, by multi-pin plug and socket connectors. Similarly, communication between the harness and power, control and signalling circuitry is achieved through a multi-pin connector.
By way of example, FIG. 1 of the accompanying drawings shows a typical gas turbine engine including two conventional wiring harnesses 102, 104, each provided with a respective connector component 106, 108 for connection to circuitry accommodated within the airframe of an aircraft in which the engine is installed. The harnesses 102, 104 are assembled from individual wires and cables which are held together over at least part of their lengths by suitable sleeving and/or braiding. Individual wires and cables, for example those indicated at 110, emerge from the sleeving or braiding to terminate at plug or socket connector components 112 for cooperation with complementary socket or plug connector components 114 on, or connected to, the respective electrical components.
Each conventional harness 102, 104 therefore comprises a multitude of insulated wires and cables. This makes the conventional harness bulky, heavy and difficult to manipulate. It is desirable to reduce the size and weight of components on gas turbine engines, particularly, for example, gas turbine engines for use on vehicles, such as aircraft.
It is proposed to replace at least a portion of, for example all of, the conventional harness with a flexible printed circuit board harness (FPCB harness). An example of a portion of such a flexible printed circuit board harness 20 is shown in FIGS. 2 to 5. FIG. 2 shows a perspective view of the FPCB harness portion, and FIGS. 3, 4, and 5 show side, top, and cross-sectional views respectively.
Such an FPCB harness 20 may comprise a flexible (for example elastically deformable) substrate 40 with conductive tracks 30 laid/formed therein. The FPCB harness 20 may thus be deformable. In the example shown in FIGS. 2 to 5, the FPCB harness 20 extends along a length in the x-direction, a width in the y-direction, and a thickness (or depth or height) in the z-direction. The x direction may be defined as the axial direction of the FPCB harness. Thus, the x-direction (and thus the z-direction) may change along the length of the FPCB harness 20 as the FPCB harness is deformed. This is illustrated in FIG. 3. The x-y surface(s) may be said to be the major surface(s) of the FPCB harness. In the example shown in FIGS. 2 to 5, the FPCB harness is deformable in the z direction. i.e. in a direction perpendicular to the major surface. FPCB harnesses may be additionally of alternatively deformable about any other direction, and/or may be twisted about any one or more of the x, y, or z directions.
The flexible substrate 40 may be a dielectric. By way of example, the substrate material may be, by way of example only, polyamide. As will be readily apparent, other suitable substrate material could alternatively be used.
The conductive tracks 30, which may be surrounded by the substrate, may be formed using any suitable conductive material, such as, by way of example only, copper, although other materials could alternatively be used. The conductive tracks 30 may be used to conduct/transfer electrical signals and/or electrical power, for example around a gas turbine engine and/or to/from components of a gas turbine engine and/or an airframe attached to a gas turbine engine. The size (for example the cross-sectional area) and/or the shape of the conductive tracks 30 may depend on the signal to be transmitted through the particular conductive track 30. Thus, the shape and/or size of the individual conductive tracks 30 may or may not be uniform in a FPCB harness 20.
The example shown in FIGS. 2 to 5 has 6 conductive tracks 30 running through the substrate 40. However, the number of conductive tracks 30 running through a substrate 40 could be fewer than 6, or greater than 6. Indeed the number of conductive tracks 30 could be far greater than 6, for example tens or hundreds of tracks, as required. As such, many electrical signals and/or power transmission lines may be incorporated into a single FPCB harness.
A single FPCB harness 20 may comprise one layer of tracks, or more than one layer of tracks, for example, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more than 10 layers of tracks. An FPCB harness may comprise significantly more than 10 layers of tracks, for example at least an order of magnitude more layers of tracks. In this regard, a layer of tracks may be defined as being a series of tracks that extend in the same x-y surface. Thus, the example shown in FIGS. 2 to 5 comprises 2 layers of tracks 30, with each layer comprising 3 tracks.
Using an FPCB harness to transmit electrical signals and/or power is therefore advantageous over a conventional harness, for example because of its reduced size, weight and/or complexity.
In order to attach a harness to a component (for example to a gas turbine engine or related airframe), a clip is required. An example of a clip that may be used to attach a conventional harness to a gas turbine engine is shown in FIG. 7. The clip 50 shown in FIG. 7 is configured to hold a cable, or a bundle of cables which form at least a part of a conventional wire cable harness. The clip 50 has a generally cylindrical outer casing 52 with a diameter 56 and a structural internal element 54 configured to provide strength to the clip 50. The clip 50 shown in FIG. 7 also has teeth 56 configured to grasp the generally cylindrical conventional cable harness, although the teeth 56 may not be present in some conventional clips.
FIGS. 8 and 9 show an alternative clip 60 for holding a conventional cable harness. The clip 60 shown in FIGS. 8 and 9 comprises two arms 64, 66 that define a space 62 therebetween for holding a conventional cable harness or bundle of cable harnesses. The space 62 defined between the two arms 64, 66 may be generally cylindrical. The two arms 64, 66 are sprung so as to be able to accommodate various diameters of conventional cable harnesses.